The present disclosure relates to a vibratory gyro-sensor and a vibratory gyro circuit for use in a vibratory gyro-sensor.
Heretofore, vibratory gyro-sensors have widely been used as a sensor for detecting an angular velocity (see, for example, Japanese Patent Laid-Open No. 2006-105896 (Paragraphs [0026] through [0030], [0049] FIGS. 1, 6) referred to as Patent Document 1 hereinafter).
As shown in FIG. 1 of Patent Document 1, the vibratory gyro-sensor disclosed in Patent document 1 has a vibratory gyro 31 and a vibratory gyro circuit. The vibratory gyro 31 includes two piezoelectric elements 33a, 33b disposed on a side surface of a vibrator 32. The vibratory gyro circuit includes an adding circuit 1, an oscillating circuit 2, a differential amplifying circuit 4, a synchronous detecting circuit 5, a phase shifting circuit 3, and a direct current amplifying circuit 6.
The oscillating circuit 2 outputs a drive signal to the vibratory gyro 31. The adding circuit 1 adds output signals from the two piezoelectric elements 33a, 33b of the vibratory gyro 31 and outputs the sum signal. The oscillating circuit 2 adjusts the amplitude and phase of the sum signal from the adding circuit 1, and supplies the adjusted signal as the drive signal to the vibratory gyro 31. The differential amplifying circuit 4 outputs a signal depending on the difference between the output signals from the two piezoelectric elements 33a, 33b. The synchronous detecting circuit 5 synchronously detects the signal output from the differential amplifying circuit 4 depending on a timing signal output from the phase shifting circuit 3. The direct current amplifying circuit 6 amplifies the signal which is synchronously detected by the synchronous detecting circuit 5 and outputs the amplified signal.
As shown in FIG. 6 of Patent Document 1, the phase shifting circuit 3 includes a phase shifting section (having an integrating circuit, an operational amplifier 65, etc.) for shifting the phase of the output signal from the adding circuit 1, and a comparator 66 for binarizing a signal output from the phase shifting section and outputting the binarized signal as the timing signal for the synchronous detecting circuit 5. A signal used as a threshold value by the comparator 66 is generally represented by a reference voltage from a peripheral circuit.